There are first the facts collected by Mr. Darwin, implying

functionally-altered structures in domestic animals. The hypothesis of

panmixia is, as we have seen, out of court; and therefore Mr. Darwin's

groups of evidences are reinstated. There is the changed ratio of

wing-bones and leg-bones in the duck; there are the drooping ears of cats

in China, of horses in Russia, of sheep in Italy, of guinea-pigs in

Germany, of goats and cattle in India, of rabbits, pigs, and dogs in all

long-civilized countries. Though artificial selection has come into play

where drooping has become a curious trait (as in rabbits), and has probably

caused the greater size of ears which has in some cases gone along with

diminished muscular power over them; yet it could not have been the

initiator, and has not been operative on animals bred for profit. Again

there are the changes produced by climate; as instance, among plants, the

several varieties of maize established in Germany and transformed in the

course of a few generations.

Facts of another class are yielded by the blind inhabitants of caverns. One

who studies the memoir by Mr. Packard on _The Cave Fauna of North America_,

&c., will be astonished at the variety of types in which degeneration or

loss of the eyes has become a concomitant of life passed in darkness. A

great increase in the force of this evidence will be recognized on learning

that absence or extreme imperfection of visual organs is found also in

creatures living in perpetual night at the bottoms of deep oceans.

Endeavours to account for these facts otherwise than by the effects of

disuse we have seen to be futile.

Kindred evidence is yielded by decrease of the jaws in those races which

have had diminished use of them--mankind and certain domestic animals.

Relative smallness in the jaws of civilized men, manifest enough on

comparison, has been proved by direct measurement. In pet dogs--pugs,

household spaniels--we find associated the same cause with the same effect.

Though there has been artificial selection, yet this did not operate until

the diminution had become manifest. Moreover there has been diminution of

the other structures concerned in biting: there are smaller muscles, feeble

zygomata, and diminished areas for insertion of muscles--traits which

cannot have resulted from selection, since they are invisible in the living

animal.

In abnormal vision produced by abnormal use of the eyes we have evidence of

another kind. That the Germans, among whom congenital short sight is

notoriously prevalent, have been made shortsighted by inheritance of

modifications due to continual reading of print requiring close attention,

is by some disputed. It is strange, however, that if there exists no causal

connexion between them, neither trait occurs without the other elsewhere.

But for the belief that there is a causal connexion we have the verifying

testimony of oculists. From Dr. Lindsay Johnson I have cited cases within

his professional experience of functionally-produced myopia transmitted to

children; and he asserts that other oculists have had like experiences.

Development of the musical faculty in the successive members of families

from which the great composers have come, as well as in the civilized races

at large, is not to be explained by natural selection. Even when it is

great, the musical faculty has not a life-saving efficiency as compared

with the average of faculties; for the most highly gifted have commonly

passed less prosperous lives and left fewer offspring than have those

possessed of ordinary abilities. Still less can it be said that the musical

faculty in mankind at large has been developed by survival of the fittest.

No one will assert that men in general have been enabled to survive and

propagate in proportion as their musical appreciation was great.

The transmission of nervous peculiarities functionally produced is alleged

by the highest authorities--Dr. Savage, president of the Neurological

Society, and Dr. Hughlings Jackson. The evidence they assign confirms, and

is confirmed by, that which the development of the musical faculty above

named supplies.

Here, then, we have sundry groups of facts directly supporting the belief

that functionally-wrought modifications descend from parents to offspring.

* * * * *

Now let us consider the position of those Darwinians who dissent from

Darwin, and who make light of all this evidence. We might naturally suppose

that their own hypothesis is unassailable. Yet, strange to say, they admit

that there is no direct proof that any species has been established by

natural selection. The proof is inferential only.

The certainty of an axiom does not give certainty to the deductions drawn

from it. That natural selection is, and always has been, operative is

incontestable. Obviously I should be the last person to deny that survival

of the fittest is a necessity: its negation is inconceivable. The

Neo-Darwinians, however, judging from their attitude, apparently assume

that firmness of the basis implies firmness of the superstructure. But

however high may be the probability of some of the conclusions drawn, none

of them can have more than probability; while some of them remain, and are

likely to remain, very questionable. Observe the difficulties.

(1) The general argument proceeds upon the analogy between natural

selection and artificial selection. Yet all know that the first cannot do

what the last does. Natural selection can do nothing more than preserve

those of which the _aggregate_ characters are most favourable to life. It

cannot pick out those possessed of one particular favourable character,

unless this is of extreme importance.

(2) In many cases a structure is of no service until it has reached a

certain development; and it remains to account for that increase of it by

natural selection which must be supposed to take place before it reaches

the stage of usefulness.

(3) Advantageous variations, not preserved in nature as they are by the

breeder, are liable to be swamped by crossing or to disappear by atavism.

Now whatever replies are made, their component propositions cannot be

necessary truths. So that the conclusion in each case, however reasonable,

cannot claim certainty: the fabric can have no stability like that of its

foundation.

When to uncertainties in the arguments supporting the hypothesis we add its

inability to explain facts of cardinal significance, as proved above, there

is I think ground for asserting that natural selection is less clearly

shown to be a factor in the origination of species than is the inheritance

of functionally-wrought changes.

* * * * *

If, finally, it is said that the mode in which functionally-wrought

changes, especially in small parts, so affect the reproductive elements as

to repeat themselves in offspring, cannot be imagined--if it be held

inconceivable that those minute changes in the organs of vision which cause

myopia can be transmitted through the appropriately-modified sperm-cells or

germ-cells; then the reply is that the opposed hypothesis presents a

corresponding inconceivability. Grant that the habit of a pointer was

produced by selection of those in which an appropriate variation in the

nervous system had occurred; it is impossible to imagine how a

slightly-different arrangement of a few nerve-cells and fibres could be

conveyed by a spermatozoon. So too it is impossible to imagine how in a

spermatozoon there can be conveyed the 480,000 independent variables

required for the construction of a single peacock's feather, each having a

proclivity towards its proper place. Clearly the ultimate process by which

inheritance is effected in either case passes comprehension; and in this

respect neither hypothesis has an advantage over the other.

APPENDIX D.

ON ALLEGED "SPONTANEOUS GENERATION," AND ON THE HYPOTHESIS OF PHYSIOLOGICAL

UNITS.

[_The following letter, originally written for publication in the_ North

American Review, _but declined by the Editor in pursuance of a general

rule, and eventually otherwise published in the United States, I have

thought well to append to this first volume of the_ Principles of Biology.

_I do this because the questions which it discusses are dealt with in this

volume; and because the further explanations it furnishes seem needful to

prevent misapprehensions._]

_The Editor of the North American Review._

SIR,

It is in most cases unwise to notice adverse criticisms. Either they do not

admit of answers or the answers may be left to the penetration of readers.

When, however, a critic's allegations touch the fundamental propositions of

a book, and especially when they appear in a periodical having the position

of the _North American Review_, the case is altered. For these reasons the

article on "Philosophical Biology," published in your last number, demands

from me an attention which ordinary criticisms do not.

It is the more needful for me to notice it, because its two leading

objections have the one an actual fairness and the other an apparent

fairness; and in the absence of explanations from me, they will be

considered as substantiated even by many, or perhaps most, of those who

have read the work itself--much more by those who have not read it. That to

prevent the spread of misapprehensions I ought to say something, is further

shown by the fact that the same two objections have already been made in

England--the one by Dr. Child, of Oxford, in his _Essays on Physiological

Subjects_, and the other by a writer in the _Westminster Review_ for July,

1865.

* * * * *

In the note to which your reviewer refers, I have, as he says, tacitly

repudiated the belief in "spontaneous generation;" and that I have done

this in such a way as to leave open the door for the interpretation given

by him is true. Indeed the fact that Dr. Child, whose criticism is a

sympathetic one, puts the same construction on this note, proves that your

reviewer has but drawn what seems to be a necessary inference.

Nevertheless, the inference is one which I did not intend to be drawn.

In explanation, let me at the outset remark that I am placed at a

disadvantage in having had to omit that part of the System of Philosophy

which deals with Inorganic Evolution. In the original programme will be

found a parenthetic reference to this omitted part, which should, as there

stated, precede the _Principles of Biology_. Two volumes are missing. The

closing chapter of the second, were it written, would deal with the

evolution of organic matter--the step preceding the evolution of living

forms. Habitually carrying with me in thought the contents of this

unwritten chapter, I have, in some cases, expressed myself as though the

reader had it before him; and have thus rendered some of my statements

liable to misconstructions. Apart from this, however, the explanation of

the apparent inconsistency is very simple, if not very obvious. In the

first place, I do not believe in the "spontaneous generation" commonly

alleged, and referred to in the note; and so little have I associated in

thought this alleged "spontaneous generation" which I disbelieve, with the

generation by evolution which I do believe, that the repudiation of the one

never occurred to me as liable to be taken for repudiation of the other.

That creatures having _quite specific structures_ are evolved in the course

of a few hours, without antecedents calculated to determine their specific

forms, is to me incredible. Not only the established truths of Biology, but

the established truths of science in general, negative the supposition that

organisms having structures definite enough to identify them as belonging

to known genera and species, can be produced in the absence of germs

derived from antecedent organisms of the same genera and species. If there

can suddenly be imposed on simple protoplasm the organization which

constitutes it a _Paramoecium_, I see no reason why animals of greater

complexity, or indeed of any complexity, may not be constituted after the

same manner. In brief, I do not accept these alleged facts as exemplifying

Evolution, because they imply something immensely beyond that which

Evolution, as I understand it, can achieve. In the second place, my

disbelief extends not only to the alleged cases of "spontaneous

generation," but to every case akin to them. The very conception of

spontaneity is wholly incongruous with the conception of Evolution. For

this reason I regard as objectionable Mr. Darwin's phrase "spontaneous

variation" (as indeed he does himself); and I have sought to show that

there are always assignable causes of variation. No form of Evolution,

inorganic or organic, can be spontaneous; but in every instance the

antecedent forces must be adequate in their quantities, kinds, and

distributions, to work the observed effects. Neither the alleged cases of

"spontaneous generation," nor any imaginable cases in the least allied to

them, fulfil this requirement.

If, accepting these alleged cases of "spontaneous generation," I had

assumed, as your reviewer seems to do, that the evolution of organic life

commenced in an analogous way; then, indeed, I should have left myself open

to a fatal criticism. This supposed "spontaneous generation" habitually

occurs in menstrua that contain either organic matter, or matter originally

derived from organisms; and such organic matter, proceeding in all known

cases from organisms of a higher kind, implies the pre-existence of such

higher organisms. By what kind of logic, then, is it inferrible that

organic life was initiated after a manner like that in which _Infusoria_

are said to be now spontaneously generated? Where, before life commenced,

were the superior organisms from which these lowest organisms obtained

their organic matter? Without doubting that there are those who, as the

reviewer says, "can penetrate deeper than Mr. Spencer has done into the

idea of universal evolution," and who, as he contends, prove this by

accepting the doctrine of "spontaneous generation"; I nevertheless think

that I can penetrate deep enough to see that a tenable hypothesis

respecting the origin of organic life must be reached by some other clue

than that furnished by experiments on decoction of hay and extract of beef.

From what I do not believe, let me now pass to what I do believe. Granting

that the formation of organic matter, and the evolution of life in its

lowest forms, may go on under existing cosmical conditions; but believing

it more likely that the formation of such matter and such forms, took place

at a time when the heat of the Earth's surface was falling through those

ranges of temperature at which the higher organic compounds are unstable; I

conceive that the moulding of such organic matter into the simplest types,

must have commenced with portions of protoplasm more minute, more

indefinite, and more inconstant in their characters, than the lowest

Rhizopods--less distinguishable from a mere fragment of albumen than even

the _Protogenes_ of Professor Haeckel. The evolution of specific shapes

must, like all other organic evolution, have resulted from the actions and

reactions between such incipient types and their environments, and the

continued survival of those which happened to have specialities best fitted

to the specialities of their environments. To reach by this process the

comparatively well-specialized forms of ordinary _Infusoria_, must, I

conceive, have taken an enormous period of time.

To prevent, as far as may be, future misapprehension, let me elaborate this

conception so as to meet the particular objections raised. The reviewer

takes for granted that a "first organism" must be assumed by me, as it is

by himself. But the conception of a "first organism," in anything like the

current sense of the words, is wholly at variance with conception of

evolution; and scarcely less at variance with the facts revealed by the

microscope. The lowest living things are not properly speaking organisms at

all; for they have no distinctions of parts--no traces of organization. It

is almost a misuse of language to call them "forms" of life: not only are

their outlines, when distinguishable, too unspecific for description, but

they change from moment to moment and are never twice alike, either in two

individuals or in the same individual. Even the word "type" is applicable

in but a loose way; for there is little constancy in their generic

characters: according as the surrounding conditions determine, they undergo

transformations now of one kind and now of another. And the vagueness, the

inconstancy, the want of appreciable structure, displayed by the simplest

of living things as we now see them, are characters (or absences of

characters) which, on the hypothesis of Evolution, must have been still

more decided when, as at first, no "forms," no "types," no "specific

shapes," had been moulded. That "absolute commencement of organic life on

the globe," which the reviewer says I "cannot evade the admission of," I

distinctly deny. The affirmation of universal evolution is in itself the

negation of an "absolute commencement" of anything. Construed in terms of

evolution, every kind of being is conceived as a product of modifications

wrought by insensible gradations on a pre-existing kind of being; and this

holds as fully of the supposed "commencement of organic life" as of all

subsequent developments of organic life. It is no more needful to suppose

an "absolute commencement of organic life" or a "first organism," than it

is needful to suppose an absolute commencement of social life and a first

social organism. The assumption of such a necessity in this last case, made

by early speculators with their theories of "social contracts" and the

like, is disproved by the facts; and the facts, so far as they are

ascertained, disprove the assumption of such a necessity in the first case.

That organic matter was not produced all at once, but was reached through

steps, we are well warranted in believing by the experiences of chemists.

Organic matters are produced in the laboratory by what we may literally

call _artificial evolution_. Chemists find themselves unable to form these

complex combinations directly from their elements; but they succeed in

forming them indirectly, by successive modifications of simpler

combinations. In some binary compound, one element of which is present in

several equivalents, a change is made by substituting for one of these

equivalents an equivalent of some other element; so producing a ternary

compound. Then another of the equivalents is replaced, and so on. For

instance, beginning with ammonia, N H_{3}, a higher form is obtained by

replacing one of the atoms of hydrogen by an atom of methyl, so producing

methyl-amine, N (C H_{3} H_{2}); and then, under the further action of

methyl, ending in a further substitution, there is reached the still more

compound substance dimethyl-amine, N (C H_{3}) (C H_{3}) H. And in this

manner highly complex substances are eventually built up. Another

characteristic of their method is no less significant. Two complex

compounds are employed to generate, by their action upon one another, a

compound of still greater complexity: different heterogeneous molecules of

one stage, become parents of a molecule a stage higher in heterogeneity.

Thus, having built up acetic acid out of its elements, and having by the

process of substitution described above, changed the acetic acid into

propionic acid, and propionic into butyric, of which the formula is

{C(CH_{3})(CH_{3})H}

{CO(HO) };

this complex compound, by operating on another complex compound, such as

the dimethyl-amine named above, generates one of still greater complexity,

butyrate of dimethyl-amine

{C(CH)(CH_{3})H} N(CH_{3})(CH_{3})H.

{CO(HO) }

See, then, the remarkable parallelism. The progress towards higher types of

organic molecules is effected by modifications upon modifications; as

throughout Evolution in general. Each of these modifications is a change of

the molecule into equilibrium with its environment--an adaptation, as it

were, to new surrounding conditions to which it is subjected; as throughout

Evolution in general. Larger, or more integrated, aggregates (for compound

molecules are such) are successively generated; as throughout Evolution in

general. More complex or heterogeneous aggregates are so made to arise, one

out of another; as throughout Evolution in general. A

geometrically-increasing multitude of these larger and more complex

aggregates so produced, at the same time results; as throughout Evolution

in general. And it is by the action of the successively higher forms on one

another, joined with the action of environing conditions, that the highest

forms are reached; as throughout Evolution in general.

When we thus see the identity of method at the two extremes--when we see

that the general laws of evolution, as they are exemplified in known

organisms, have been unconsciously conformed to by chemists in the

artificial evolution of organic matter; we can scarcely doubt that these

laws were conformed to in the natural evolution of organic matter, and

afterwards in the evolution of the simplest organic forms. In the early

world, as in the modern laboratory, inferior types of organic substances,

by their mutual actions under fit conditions, evolved the superior types of

organic substances, ending in organizable protoplasm. And it can hardly be

doubted that the shaping of organizable protoplasm, which is a substance

modifiable in multitudinous ways with extreme facility, went on after the

same manner. As I learn from one of our first chemists, Prof. Frankland,

_protein_ is capable of existing under probably at least a thousand

isomeric forms; and, as we shall presently see, it is capable of forming,

with itself and other elements, substances yet more intricate in

composition, that are practically infinite in their varieties of kind.

Exposed to those innumerable modifications of conditions which the Earth's

surface afforded, here in amount of light, there in amount of heat, and

elsewhere in the mineral quality of its aqueous medium, this extremely

changeable substance must have undergone now one, now another, of its

countless metamorphoses. And to the mutual influences of its metamorphic

forms under favouring conditions, we may ascribe the production of the

still more composite, still more sensitive, still more variously-changeable

portions of organic matter, which, in masses more minute and simpler than

existing _Protozoa_, displayed actions verging little by little into those

called vital--actions which protein itself exhibits in a certain degree,

and which the lowest known living things exhibit only in a greater degree.

Thus, setting out with inductions from the experiences of organic chemists

at the one extreme, and with inductions from the observations of biologists

at the other extreme, we are enabled deductively to bridge the

interval--are enabled to conceive how organic compounds were evolved, and

how, by a continuance of the process, the nascent life displayed in these

became gradually more pronounced. And this it is which has to be explained,

and which the alleged cases of "spontaneous generation" would not, were

they substantiated, help us in the least to explain.

It is thus manifest, I think, that I have not fallen into the alleged

inconsistency. Nevertheless, I admit that your reviewer was justified in

inferring this inconsistency; and I take blame to myself for not having

seen that the statement, as I have left it, is open to misconstruction.

* * * * *

I pass now to the second allegation--that in ascribing to certain specific

molecules, which I have called "physiological units," the aptitude to build

themselves into the structure of the organism to which they are peculiar, I

have abandoned my own principle, and have assumed something beyond the

re-distribution of Matter and Motion. As put by the reviewer, his case

appears to be well made out; and that he is not altogether unwarranted in

so putting it, may be admitted. Nevertheless, there does not in reality

exist the supposed incongruity.

Before attempting to make clear the adequacy of the conception which I am

said to have tacitly abandoned as insufficient, let me remove that excess

of improbability the reviewer gives to it, by the extremely-restricted

meaning with which he uses the word mechanical. In discussing a proposition

of mine he says:--

"He then cites certain remarks of Mr. Paget on the permanent effects

wrought in the blood by the poison of scarlatina and small-pox, as

justifying the belief that such a 'power' exists, and attributes the

repair of a wasted tissue to 'forces analogous to those by which a

crystal reproduces its lost apex.' (Neither of which phenomena, however,

is explicable by mechanical causes.)"

Were it not for the deliberation with which this last statement is made, I

should take it for a slip of the pen. As it is, however, I have no course

left but to suppose the reviewer unaware of the fact that molecular actions

of all kinds are now not only conceived as mechanical actions, but that

calculations based on this conception of them, bring out the results that

correspond with observation. There is no kind of re-arrangement among

molecules (crystallization being one) which the modern physicist does not

think of. and correctly reason upon, in terms of forces and motions like

those of sensible masses. Polarity is regarded as a resultant of such

forces and motions; and when, as happens in many cases, light changes the

molecular structure of a crystal, and alters its polarity, it does this by

impressing, in conformity with mechanical laws, new motions on the

constituent molecules. That the reviewer should present the mechanical

conception under so extremely limited a form, is the more surprising to me

because, at the outset of the very work he reviews, I have, in various

passages, based inferences on those immense extensions of it which he

ignores; indicating, for example, the interpretation it yields of the

inorganic chemical changes effected by heat, and the organic chemical

changes effected by light (_Principles of Biology_, § 13).

Premising, then, that the ordinary idea of mechanical action must be

greatly expanded, let us enter upon the question at issue--the sufficiency

of the hypothesis that the structure of each organism is determined by the

polarities of the special molecules, or physiological units, peculiar to it

as a species, which necessitate tendencies towards special arrangements. My

proposition and the reviewer's criticism upon it, will be most conveniently

presented if I quote in full a passage of his from which I have already

extracted some expressions. He says:--

"It will be noticed, however, that Mr. Spencer attributes the possession

of these 'tendencies,' or 'proclivities,' to natural inheritance from

ancestral organisms; and it may be argued that he thus saves the

mechanist theory and his own consistency at the same time, inasmuch as he

derives even the 'tendencies' themselves ultimately from the environment.

To this we reply, that Mr. Spencer, who advocates the nebular hypothesis,

cannot evade the admission of an absolute commencement of organic life on

the globe, and that the 'formative tendencies,' without which he cannot

explain the evolution of a single individual, could not have been

inherited by the first organism. Besides, by his virtual denial of

spontaneous generation, he denies that the first organism was evolved out

of the inorganic world, and thus shuts himself off from the argument

(otherwise plausible) that its 'tendencies' were ultimately derived from

the environment."

This assertion is already in great measure disposed of by what has been

said above. Holding that, though not "spontaneously generated," those

minute portions of protoplasm which first displayed in the feeblest degree

that changeability taken to imply life, were evolved, I am _not_ debarred

from the argument that the "tendencies" of the physiological units are

derived from the inherited effects of environing actions. If the conception

of a "first organism" were a necessary one, the reviewer's objection would

be valid. If there were an "absolute commencement" of life, a definite line

parting organic matter from the simplest living forms, I should be placed

in the predicament he describes. But as the doctrine of Evolution itself

tacitly negatives any such distinct separation; and as the negation is the

more confirmed by the facts the more we know of them; I do not feel that I

am entangled in the alleged difficulty. My reply might end here; but as the

hypothesis in question is one not easily conceived, and very apt to be

misunderstood, I will attempt a further elucidation of it.

Much evidence now conspires to show that molecules of the substances we

call elementary are in reality compound; and that, by the combination of

these with one another, and re-combinations of the products, there are

formed systems of systems of molecules, unimaginable in their complexity.

Step by step as the aggregate molecules so resulting, grow larger and

increase in heterogeneity, they become more unstable, more readily

transformable by small forces, more capable of assuming various characters.

Those composing organic matter transcend all others in size and intricacy

of structure; and in them these resulting traits reach their extreme. As

implied by its name _protein_, the essential substance of which organisms

are built, is remarkable alike for the variety of its metamorphoses and the

facility with which it undergoes them: it changes from one to another of

its thousand isomeric forms on the slightest change of conditions. Now

there are facts warranting the belief that though these multitudinous

isomeric forms of protein will not unite directly with one another, yet

they admit of being linked together by other elements with which they

combine. And it is very significant that there are habitually present two

other elements, sulphur and phosphorus, which have quite special powers of

holding together many equivalents--the one being pentatomic and the other

hexatomic. So that it is a legitimate supposition (justified by analogies)

that an atom of sulphur may be a bond of union among half-a-dozen different

isomeric forms of protein; and similarly with phosphorus. A moment's

thought will show that, setting out with the thousand isomeric forms of

protein, this makes possible a number of these combinations almost passing

the power of figures to express. Molecules so produced, perhaps exceeding

in size and complexity those of protein as those of protein exceed those of

inorganic matter, may, I conceive, be the special units belonging to

special kinds of organisms. By their constitution they must have a

plasticity, or sensitiveness to modifying forces, far beyond that of

protein; and bearing in mind not only that their varieties are practically

infinite in number, but that closely allied forms of them, chemically

indifferent to one another as they must be, may coexist in the same

aggregate, we shall see that they are fitted for entering into unlimited

varieties of organic structures.

The existence of such physiological units, peculiar to each species of

organism, is not unaccounted for. They are evolved simultaneously with the

evolution of the organisms they compose--they differentiate as fast as

these organisms differentiate; and are made multitudinous in kind by the

same actions which make the organism they compose multitudinous, in kind.

This conception is clearly representable in terms of the mechanical

hypothesis. Every physicist will endorse the proposition that in each

aggregate there tends to establish itself an equilibrium between the forces

exercised by all the units upon each and by each upon all. Even in masses

of substance so rigid as iron and glass, there goes on a molecular

re-arrangement, slow or rapid according as circumstances facilitate, which

ends only when there is a complete balance between the actions of the parts

on the whole and the actions of the whole on the parts: the implications

being that every change in the form or size of the whole, necessitates some

redistribution of the parts. And though in cases like these, there occurs

only a polar re-arrangement of the molecules, without changes in the

molecules themselves; yet where, as often happens, there is a passage from

the colloid to the crystalloid state, a change of constitution occurs in

the molecules themselves. These truths are not limited to inorganic matter:

they unquestionably hold of organic matter. As certainly as molecules of

alum have a form of equilibrium, the octahedron, into which they fall when

the temperature of their solvent allows them to aggregate, so certainly

must organic molecules of each kind, no matter how complex, have a form of

equilibrium in which, when they aggregate, their complex forces are

balanced--a form far less rigid and definite, for the reason that they have

far less definite polarities, are far more unstable, and have their

tendencies more easily modified by environing conditions. Equally certain

is it that the special molecules having a special organic structure as

their form of equilibrium, must be reacted upon by the total forces of this

organic structure; and that, if environing actions lead to any change in

this organic structure, these special molecules, or physiological units,

subject to a changed distribution of the total forces acting upon them will

undergo modification--modification which their extreme plasticity will

render easy. By this action and reaction I conceive the physiological units

peculiar to each kind of organism, to have been moulded along with the

organism itself. Setting out with the stage in which protein in minute

aggregates, took on those simplest differentiations which fitted it for

differently-conditioned parts of its medium, there must have unceasingly

gone on perpetual re-adjustments of balance between aggregates and their

units--actions and reactions of the two, in which the units tended ever to

establish the typical form produced by actions and reactions in all

antecedent generations, while the aggregate, if changed in form by change

of surrounding conditions, tended ever to impress on the units a

corresponding change of polarity, causing them in the next generation to

reproduce the changed form--their new form of equilibrium.

This is the conception which I have sought to convey, though it seems

unsuccessfully, in the _Principles of Biology_; and which I have there used

to interpret the many involved and mysterious phenomena of Genesis,

Heredity, and Variation. In one respect only am I conscious of having so

inadequately explained myself, as to give occasion for a

misinterpretation--the one made by the _Westminster_ reviewer above

referred to. By him, as by your own critic, it is alleged that in the idea

of "inherent tendencies" I have introduced, under a disguise, the

conception of "the archæus, vital principle, _nisus formativus_, and so

on." This allegation is in part answered by the foregoing explanation. That

which I have here to add, and did not adequately explain in the _Principles

of Biology_, is that the proclivity of units of each order towards the

specific arrangement seen in the organism they form, is not to be

understood as resulting from their own structures and actions only; but as

the product of these and the environing forces to which they are exposed.

Organic evolution takes place only on condition that the masses of

protoplasm formed of the physiological units, and of the assimilable

materials out of which others like themselves are to be multiplied, are

subject to heat of a given degree--are subject, that is, to the unceasing

impacts of undulations of a certain strength and period; and, within

limits, the rapidity with which the physiological units pass from their

indefinite arrangement to the definite arrangement they presently assume,

is proportionate to the strengths of the ethereal undulations falling upon

them. In its complete form, then, the conception is that these specific

molecules, having the immense complexity above described, and having

correspondently complex polarities which cannot be mutually balanced by any

simple form of aggregation, have, for the form of aggregation in which all

their forces are equilibrated, the structure of the adult organism to which

they belong; and that they are compelled to fall into this structure by the

co-operation of the environing forces acting on them, and the forces they

exercise on one another--the environing forces being the source of the

_power_ which effects the re-arrangement, and the polarities of the

molecules determining the _direction_ in which that power is turned. Into

this conception there enters no trace of the hypothesis of an "archæus or

vital principle;" and the principles of molecular physics fully justify it.

It is, however, objected that "the living body in its development presents

a long succession of _differing_ forms; a continued series of changes for

the whole length of which, according to Mr. Spencer's hypothesis, the

physiological units must have an 'inherent tendency.' Could we more truly

say of anything, 'it is unrepresentable in thought?'" I reply that if there

is taken into account an element here overlooked, the process will not be

found "unrepresentable in thought." This is the element of size or mass. To

satisfy or balance the polarities of each order of physiological units, not

only a certain structure of organism, but a certain size of organism is

needed; for the complexities of that adult structure in which the

physiological units are equilibrated, cannot be represented within the

small bulk of the embryo. In many minute organisms, where the whole mass of

physiological units required for the structure is present, the very thing

_does_ take place which it is above implied _ought_ to take place. The mass

builds itself directly into the complete form. This is so with _Acari_, and

among the nematoid _Entozoa_. But among higher animals such direct

transformations cannot happen. The mass of physiological units required to

produce the size as well as the structure that approximately equilibrates

them, is not all present, but has to be formed by successive

additions--additions which in viviparous animals are made by absorbing, and

transforming into these special molecules, the organizable materials

directly supplied by the parent, and which in oviparous animals are made by

doing the like with the organizable materials in the "food-yelk," deposited

by the parent in the same envelope with the germ. Hence it results that,

under such conditions, the physiological units which first aggregate into

the rudiment of the future organism, do not form a structure like that of

the adult organism, which, when of such small dimensions, does not

equilibrate them. They distribute themselves so as partly to satisfy the

chief among their complex polarities. The vaguely-differentiated mass thus

produced cannot, however, be in equilibrium. Each increment of

physiological units formed and integrated by it, changes the distribution

of forces; and this has a double effect. It tends to modify the

differentiations already made, bringing them a step nearer to the

equilibrating structure; and the physiological units next integrated, being

brought under the aggregate of polar forces exercised by the whole mass,

which now approaches a step nearer to that ultimate distribution of polar

forces which exists in the adult organism, are coerced more directly into

the typical structure. Thus there is necessitated a series of compromises.

Each successive form assumed is unstable and transitional: approach to the

typical structure going on hand in hand with approach to the typical bulk.

Possibly I have not succeeded by this explanation, any more than by the

original explanation, in making this process "representable in thought." It

is manifestly untrue, however, that I have, as alleged, re-introduced under

a disguise the conception of a "vital principle." That I interpret

embryonic development in terms of Matter and Motion, cannot, I think, be

questioned. Whether the interpretation is adequate, must be a matter of

opinion; but it is clearly a matter of fact, that I have not fallen into

the inconsistency asserted by your reviewer. At the same time I willingly

admit that, in the absence of certain statements which I have now supplied,

he was not unwarranted in representing my conception in the way that he has

done.

----

NOTES

[1] Gross misrepresentations of this statement, which have been from time

to time made, oblige me, much against my will, to add here an

explanation of it. The last of these perversions, uttered in a

lecture delivered at Belfast by the Rev. Professor Watts, D.D., is

reported in the _Belfast Witness_ of December 18, 1874; just while a

third impression of this work is being printed from the plates. The

report commences as follows:--"Dr. Watts, after showing that on his

own confession Spencer was indebted for his facts to Huxley and

Hooker, who," &c., &c.

Wishing in this, as in other cases, to acknowledge indebtedness when

conscious of it, I introduced the words referred to, in recognition

of the fact that I had repeatedly questioned the distinguished

specialists named, on matters beyond my knowledge, which were not

dealt with in the books at my command. Forgetting the habits of

antagonists, and especially theological antagonists, it never

occurred to me that my expression of thanks to my friends for

"information where my own was deficient," would be turned into the

sweeping statement that I was indebted to them for my facts.

Had Professor Watts looked at the preface to the second volume (the

two having been published separately, as the prefaces imply), he

would have seen a second expression of my indebtedness "for their

valuable criticisms, and for the trouble they have taken in

_checking_ the numerous statements of fact on which the arguments

proceed"--no further indebtedness being named. A moment's comparison

of the two volumes in respect of their accumulations of facts, would

have shown him what kind of warrant there was for his interpretation.

Doubtless the Rev. Professor was prompted to make this assertion by

the desire to discredit the work he was attacking; and having so good

an end in view, thought it needless to be particular about the means.

In the art of dealing with the language of opponents, Dr. Watts might

give lessons to Monsignor Capel and Archbishop Manning.

_December 28th, 1874._

[2] In this passage as originally written (in 1862) they were described

as incondensible; since, though reduced to the density of liquids,

they had not been liquefied.

[3] Here and hereafter the word "atom" signifies a unit of something

classed as an element, because thus far undecomposed by us. The word

must not be supposed to mean that which its derivation implies. In

all probability it is not a simple unit but a compound one.

[4] The name hydro-carbons was here used when these pages were written,

thirty-four years ago. It was the name then current. In this case, as

in multitudinous other cases, the substitution of newer words and

phrases for older ones, is somewhat misleading. Putting the thoughts

of 1862 in the language of 1897 gives an illusive impression of

recency.

[5] It will perhaps seem strange to class oxygen as a crystalloid. But

inasmuch as the crystalloids are distinguished from the colloids by

their atomic simplicity, and inasmuch as sundry gases are reducible

to a crystalline state, we are justified in so classing it.

[6] The remark made by a critic to the effect that in a mammal higher

temperature diminishes the rate of molecular change in the tissues,

leads me to add that the exhalation I have alleged is prevented if

the heat rises above the range of variation normal to the organism;

since, then, unusually rapid pulsations with consequent inefficient

propulsion of the blood, cause a diminished rate of circulation. To

produce the effect referred to in the text, heat must be associated

with dryness; for otherwise evaporation is not aided. General

evidence supporting the statement I have made is furnished by the

fact that the hot and dry air of the eastern deserts is extremely

invigorating; by the fact that all the energetic and conquering races

of men have come from the hot and dry regions marked on the maps as

rainless; and by the fact that travellers in Africa comment on the

contrast between the inhabitants of the hot and dry regions

(relatively elevated) and those of the hot and moist regions: active

and inert respectively.

[7] The increase of respiration found to result from the presence of

light, is probably an _indirect_ effect. It is most likely due to the

reception of more vivid impressions through the eyes, and to the

consequent nervous stimulation. Bright light is associated in our

experience with many of our greatest outdoor pleasures, and its

presence partially arouses the consciousness of them, with the

concomitant raised vital functions.

[8] To exclude confusion it may be well here to say that the word "atom"

is, as before explained, used as the name for a unit of a substance

at present undecomposed; while the word "molecule" is used as the

name for a unit of a substance known to be compound.

[9] On now returning to the subject after many years, I meet with some

evidence recently assigned, in a paper read before the Royal Society

by Mr. J. W. Pickering, D.Sc. (detailing results harmonizing with

those obtained by Prof. Grimaux), showing clearly how important an

agent in vital actions is this production of isomeric changes by

slight changes of conditions. Certain artificially produced

substances, simulating proteids in other of their characters and

reactions, were found to simulate them in coagulability by trifling

disturbances. "In the presence of a _trace of neutral salt_ they

coagulate on heating at temperatures very similar to proteid

solutions." And it is shown that by one of these factitious organic

colloids a like effect is produced in coagulating the blood, to that

"produced by the intravenous injection of a nucleoproteid."

[10] After this long interval during which other subjects have occupied

me, I now find that the current view is similar to the view above set

forth, in so far that a small molecular disturbance is supposed

suddenly to initiate a great one, producing a change compared to an

explosion. But while, of two proposed interpretations, one is that

the fuse is nitrogenous and the charge a carbo-hydrate, the other is

that both are nitrogenous. The relative probabilities of these

alternative views will be considered in a subsequent chapter.

[11] When writing this passage I omitted to observe the verification

yielded of the conclusion contained in § 15 concerning the part

played in the vital processes by the nitrogenous compounds. For these

vegeto-alkalies, minute quantities of which produce such great

effects in exalting the functions (_e. g._, a sixteenth of a grain of

strychnia is a dose), are all nitrogenous bodies, and, by

implication, relatively unstable bodies. The small amounts of

molecular change which take place in these small quantities of the

vegeto-alkalies when diffused through the system, initiate larger

amounts of molecular change in the nitrogenous elements of the

tissues.

But the evidence furnished a generation ago by these vegeto-alkalies

has been greatly reinforced by far more striking evidence furnished

by other nitrogenous compounds--the various explosives. These, at the

same time that they produce by their sudden decompositions violent

effects outside the organism, also produce violent effects inside it:

a hundredth of a grain of nitro-glycerine being a sufficient dose.

Investigations made by Dr. J. B. Bradbury, and described by him in

the Bradshaw Lecture on "Some New Vaso-Dilators" (see _The Lancet_,

Nov. 16, 1895), details the effects of kindred

bodies--methyl-nitrate, glycol-dinitrate, erythrol-tetranitrate. The

first two, in common with nitro-glycerine, are stable only when cool

and in the dark--sunlight or warmth decomposes them, and they explode

by rapid heating or percussion. The fact which concerns us here is

that the least stable--glycol-dinitrate--has the most powerful and

rapid physiological effect, which is proportionately transient. In

one minute the blood-pressure is reduced by one-fourth and in four

minutes by nearly two-thirds: an effect which is dissipated in a

quarter of an hour. So that this excessively unstable compound,

decomposing in the body in a very short time, produces within that

short time a vast amount of molecular change: acting, as it seems,

not through the nervous system, but directly on the blood-vessels.

[12] This interpretation is said to be disproved by the fact that the

carbo-hydrate contained in muscle amounts to only about 1.5 of the

total solids. I do not see how this statement is to be reconciled

with the statement cited three pages back from Professor Michael

Foster, that the deposits of glycogen contained in the liver and in

the muscles may be compared to the deposits in a central bank and

branch banks.

[13] Before leaving the topic let me remark that the doctrine of

metabolism is at present in its inchoate stage, and that the

prevailing conclusions should be held tentatively. As showing this

need an anomalous fact may be named. It was long held that gelatine

is of small value as food, and though it is now recognized as

valuable because serving the same purposes as fats and

carbo-hydrates, it is still held to be valueless for structural

purposes (save for some inactive tissue); and this estimate agrees

with the fact that it is a relatively stable nitrogenous compound,

and therefore unfit for those functions performed by unstable

nitrogenous compounds in the muscular and other tissues. But if this

is true, it seems a necessary implication that such substances as

hair, wool, feathers, and all dermal growths chemically akin to

gelatine, and even more stable, ought to be equally innutritive or

more innutritive. In that case, however, what are we to say of the

larva of the clothes-moth, which subsists exclusively on one or other

of these substances, and out of it forms all those unstable

nitrogenous compounds needful for carrying on its life and developing

its tissues? Or again, how are we to understand the nutrition of the

book-worm, which, in the time-stained leaves through which it

burrows, finds no proteid save that contained in the dried-up size,

which is a form of gelatine; or, once more, in what form is the

requisite amount of nitrogenous substance obtained by the

coleopterous larva which eats holes in wood a century old?

[14] This chapter and the following two chapters originally appeared in

Part III of the original edition of the _Principles of Psychology_

(1855): forming a preliminary which, though indispensable to the

argument there developed, was somewhat parenthetical. Having now to

deal with the general science of Biology before the more special one

of Psychology, it becomes possible to transfer these chapters to

their proper place.

[15] See _Westminster Review_ for April, 1852.--Art. IV. "A Theory of

Population." See Appendix A.

[16] This paragraph replaces a sentence that, in _The Principles of

Psychology_, referred to a preceding chapter on "Method;" in which

the mode of procedure here indicated was set forth as a mode to be

systematically pursued in the choice of hypotheses. This chapter on

Method is now included, along with other matter, in a volume entitled

_Various Fragments_.

[17] Speaking of "the general idea of _life_" M. Comte says:--"Cette idée

suppose, en effet, non-seulement celle d'un être organisé de manière

à comporter l'état vital, mais aussi celle, non moins indispensable,

d'un certain ensemble d'influences extérieures propres à son

accomplissement. Une telle harmonie entre l'être vivant et le

_milieu_ correspondant, caractérise evidemment la condition

fondamentale de la vie." Commenting on de Blainville's definition of

life, which he adopts, he says:--"Cette lumineuse définition ne me

paraît laisser rien d'important à désirer, si ce n'est une indication

plus directe et plus explicite de ces deux conditions fondamentales

co-relatives, nécessairement inséparables de l'état vivant, un

_organisme_ déterminé et un _milieu_ convenable." It is strange that

M. Comte should have thus recognized the necessity of a harmony

between an organism and its environment, as a _condition_ essential

to life, and should not have seen that the continuous maintenance of

such inner actions as will counterbalance outer actions,

_constitutes_ life.

[When the original edition was published Dr. J. H. Bridges wrote to

me saying that in the _Politique Positive_, Comte had developed his

conception further. On p. 413, denying "le prétendu antagonisme des

corps vivants envers leurs milieux inorganiques," he says "au lieu de

ce conflit, on a reconnu bientôt que cette relation nécessaire

constitue une condition fondamentale de la vie réelle, dont la notion

systématique consiste dans une intime conciliation permanente entre

la spontanéité intérieure et la fatalité extérieure." Still, this

"conciliation _permanente_" seems to be a "_condition_" to life; not

that varying adjustment of changes which life consists in

maintaining. In presence of an ambiguity, the interpretation which

agrees with his previous statement must be chosen.]

[18] In further elucidation of this general doctrine, see _First

Principles_, § 25.

[19] In ordinary speech Development is often used as synonymous with

Growth. It hence seems needful to say that Development as here and

hereafter used, means _increase of structure_ and not _increase of

bulk_. It may be added that the word Evolution, comprehending growth

as well as Development, is to be reserved for occasions when both are

implied.

[20] This paragraph originally formed part of a review-article on

"Transcendental Physiology," published in 1857.

[21] When, in 1863, the preceding chapter was written, it had not occurred

to me that there needed an accompanying chapter treating of

Structure. The gap left by that oversight I now fill up. In doing

this there have been included certain statements which are tacitly

presupposed in the last chapter, and there may also be some which

overlap statements in the next chapter. I have not thought it needful

so to alter adjacent chapters as to remove these slight defects: the

duplicated ideas will bear re-emphasizing.

[22] In connexion with this matter I add here a statement made by Prof.

Foster which it is difficult to understand: "Indeed it has been

observed that a dormouse actually gained in weight during a

hybernating period; it discharged during this period neither urine

nor fæces, and the gain in weight was the excess of oxygen taken in

over the carbonic acid given out." (_Text-book of Physiology_, 6th

ed., Part II, page 859.)

[23] In the account of James Mitchell, a boy born blind and deaf, given by

James Wardrop, F.R.S. (Edin. 1813), it is said that he acquired a

"preternatural acuteness of touch and smell." The deaf Dr. Kitto

described himself as having an extremely strong visual memory: he

retained "a clear impression or image of everything at which he ever

looked."

[24] Here, as in sundry places throughout this chapter, the necessities of

the argument have obliged me to forestall myself, by assuming the

conclusion reached in a subsequent chapter, that modifications of

structure produced by modifications of function are transmitted to

offspring.

[25] Whether the _Volvox_ is to be classed as animal or vegetal is a

matter of dispute; but its similarity to the blastula stage of many

animals warrants the claim of the zoologists.

[26] While the proof was in my hands there was published in _Science

Progress_ an essay by Dr. T. G. Brodie on "The Phosphorus-containing

Substances of the Cell." In this essay it is pointed out that

"nucleic acid is particularly characterized by its instability.... In

the process of purification it is extremely liable to decompose, with

the result that it loses a considerable part of its phosphorus. In

the second place it is most easily split up in another manner in

which it loses a considerable part of its nitrogen.... To avoid the

latter source of error he [Miescher] found that it was necessary to

keep the temperature of all solutions down to 0°C., the whole time of

the preparation." These facts tend strongly to verify the hypothesis

that the nucleus is a source of perpetual molecular disturbance--not

a regulating centre but a stimulating centre.

[27] The writing of the above section reminded me of certain allied views

which I ventured to suggest nearly 50 years ago. They are contained

in the _Westminster Review_ for April, 1852, in an article entitled

"A Theory of Population deduced from the General Law of Animal

Fertility." It is there suggested that the "spermatozoon is

essentially a neural element, and the ovum essentially a hæmal

element," or, as otherwise stated, that the "sperm-cell is

co-ordinating matter and the germ-cell matter to be co-ordinated"

(pp. 490-493). And along with this proposition there is given some

chemical evidence tending to support it. Now if, in place of "neural"

and "hæmal," we say--the element that is most highly phosphorized and

the element that is phosphorized in a much smaller degree; or if, in

place of co-ordinating matter and matter to be co-ordinated, we

say--the matter which initiates action and the matter which is made

to act; there is disclosed a kinship between this early view and the

view just set forth. In the last part of this work, "Laws of

Multiplication," which is developed from the essay referred to, I

left out the portion containing the quoted sentences, and the

evidence supporting the conclusion drawn. Partly I omitted them

because the speculation did not form an essential link in the general

argument, and partly because I did not see how the suggested

interpretation could hold of plants as well as of animals. If,

however, the alleged greater staining capacity of the male generative

nucleus in plants implies, as in other cases, that the male cell has

a larger proportion of the phosphorized matter than the other

elements concerned, then the difficulty disappears.

As, along with the idea just named, the dropped portion of the

original essay contains other ideas which seem to me worth

preserving, I have thought it as well to reproduce it, in company

with the chief part of the general argument as at first sketched out.

It will be found in Appendix A to this volume.

[28] Unfortunately the word _heterogenesis_ has been already used as a

synonym for "spontaneous generation." Save by those few who believe

in "spontaneous generation," however, little objection will be felt

to using the word in a sense that seems much more appropriate. The

meaning above given to it covers both Metagenesis and

Parthenogenesis.

[29] Prof. Huxley avoids this difficulty by making every kind of Genesis a

mode of development. His classification, which suggested the one

given above, is as follows:--

{ Growth

{ Continuous {

{ { Metamorphosis

{

Development {

{ { Metagenesis

{ { Agamogenesis {

{ Discontinuous { { Parthenogenesis

{ Gamogenesis

[30] The implication is that an essentially similar process occurs in

those fragments of leaves used for artificial propagation. Besides

the Begonias in general, I learn that various other plants are thus

multiplied--Citron and orange trees, _Hoya carnosa_, _Aucuba

japonica_, _Clianthus puniceus_, etc., etc. _Bryophyllum calicinum_,

_Rochea falcata_, and _Echeveria_. I also learn that the following

plants, among others, produce buds from their foliage

leaves:--_Cardamine pratensis_, _Nasturtium officinale_, _Roripa

palustris_, _Brassica oleracea_, _Arabis pumila_, _Chelidonium

majus_, _Nymphæa guianensis_, _Episcia bicolor_, _Chirita sivensis_,

_Pinguicula Backeri_, _Allium_, _Gagea_, _Tolmia_, _Fritillaria_,

_Ornithogalum_, etc. In _Cardamine_ and several others, a complete

miniature plant is at once produced; in other cases bulbils or

similar detachable buds.

[31] Among various examples I have observed, the most remarkable were

among Foxgloves, growing in great numbers and of large size, in a

wood between Whatstandwell Bridge and Crich, in Derbyshire. In one

case the lowest flower on the stem contained, in place of a pistil, a

shoot or spike of flower-buds, similar in structure to the

embryo-buds of the main spike. I counted seventeen buds on it; of

which the first had three stamens, but was otherwise normal; the

second had three; the third, four; the fourth, four; &c. Another

plant, having more varied monstrosities, evinced excess of nutrition

with equal clearness. The following are the notes I took of its

structure:--1st, or lowest flower on the stem, very large; calyx

containing eight divisions, one partly transformed into a corolla,

and another transformed into a small bud with bract (this bud

consisted of a five-cleft calyx, four sessile anthers, a pistil, and

a rudimentary corolla); the corolla of the main flower, which was

complete, contained six stamens, three of them bearing anthers, two

others being flattened and coloured, and one rudimentary; there was

no pistil but, _in place of it_, a large bud, consisting of a

three-cleft calyx of which two divisions were tinted at the ends, an

imperfect corolla marked internally with the usual purple spots and

hairs, three anthers sessile on this mal-formed corolla, a pistil, a

seed vessel with ovules, and, growing to it, another bud of which the

structure was indistinct. 2nd flower, large; calyx of seven

divisions, one being transformed into a bud with bract, but much

smaller than the other; corolla large but cleft along the top; six

stamens with anthers, pistil, and seed-vessel. 3rd flower, large;

six-cleft calyx, cleft corolla, with six stamens, pistil, and

seed-vessel, with a second pistil half unfolded at its apex. 4th

flower, large; divided along the top, six stamens. 5th flower, large;

corolla divided into three parts, six stamens. 6th flower, large;

corolla cleft, calyx six cleft, the rest of the flower normal. 7th,

and all succeeding flowers, normal.

While this chapter is under revision, another noteworthy illustration

has been furnished to me by a wall-trained pear tree which was

covered in the spring by luxuriant "foreright" shoots. As I learned

from the gardener, it was pruned just as the fruit was setting. A

large excess of sap was thus thrown into other branches, with the

result that in a number of them the young pears were made monstrous

by reversion. In some cases, instead of the dried up sepals at the

top of the pear, there were produced good sized leaves; and in other

cases the seed-bearing core of the pear was transformed into a growth

which protruded through the top of the pear in the shape of a new

shoot.

[32] In partial verification, Mr. Tansley writes:--"Prof. Klebs of Basel

has shown that in _Hydrodictyon_, gametes can only be produced by the

cells of a net when these are above a certain size and age; and then

only under conditions unfavourable to growth, such as a feeble light

or poverty of nutritive inorganic salts or absence of oxygen, or a

low temperature in the water containing the plant. The presence of

organic substances, especially sugar, also acts as a stimulus to the

formation of gametes, and this is also the case in _Vaucheria_. Many

other _Algæ_ produce gametes mainly at the end of the vegetative

season, when food is certainly difficult to obtain in their natural

habitat, and we may well suppose that their assimilative power is

waning. Where, however, as is the case in _Vaucheria_, the plant

depends for propagation mainly on the production of fertilized eggs,

we find the sexual organs often produced in conditions very

favourable to vegetative growth, in opposition to those cases such as

_Hydrodictyon_, where the chief means of propagation is by zoospores.

So that side by side with, and to some extent obscuring, the

principle developed above we have a clear adaptation of the

production of reproductive cells to the special circumstances of the

case."

[33] This establishment by survival of the fittest of reproductive

processes adapted to variable conditions, is indirectly elucidated by

the habits of salmon. As salmon thrive in the sea and fall out of

condition in fresh water (having during their sea-life not exercised

the art of catching fresh-water prey), the implication is that the

species would profit if all individuals ran up the rivers just before

spawning time in November. Why then do most of them run up during

many preceding months? Contemplation of the difficulties which lie in

the way to the spawning grounds, will, I think, suggest an

explanation. There are falls to be leaped and shallow rapids to be

ascended. These obstacles cannot be surmounted when the river is low.

A fish which starts early in the season has more chances of getting

up the falls and the rapids than one which starts later; and, out of

condition as it will be, may spawn, though not well. On the other

hand, one which starts in October, if floods occur appropriately, may

reach the upper waters and then spawn to great advantage; but in the

absence of adequate rains it may fail altogether to reach the

spawning grounds. Hence the species profits by an irregularity of

habits adapted to meet irregular contingencies.

[34] I owe to Mr. (now Sir John) Lubbock an important confirmation of this

view. After stating his belief that between Crustaceans and Insects

there exists a physiological relation analogous to that which exists

between water vertebrata and land-vertebrata, he pointed out to me

that while among Insects there is a definite limit of growth, and an

accompanying definite commencement of reproduction, among

Crustaceans, where growth has no definite limit, there is no definite

relation between the commencement of reproduction and the decrease or

arrest of growth.

[35] While this chapter is passing through the press, I learn from Mr.

White Cooper, that not only are near sight, long sight, dull sight,

and squinting, hereditary; but that a peculiarity of vision confined

to one eye is frequently transmitted: re-appearing in the same eye in

offspring.

[36] An instance here occurs of the way in which those who are averse to a

conclusion will assign the most flimsy reasons for rejecting it.

Rather than admit that the eyes of these creatures living in darkness

have disappeared from lack of use, some contend that such creatures

would be liable to have their eyes injured by collisions with

objects, and that therefore natural selection would favour those

individuals in which the eyes had somewhat diminished and were least

liable to injury: the implication being that the immunity from the

inflammations due to injuries would be so important a factor in life

as to cause survival. And this is argued in presence of the fact that

one of the most conspicuous among these blind cave-animals is a

cray-fish, and that the cray-fish in its natural habitat is in the

habit of burrowing in the banks of rivers holes a foot or more deep,

and has its eyes exposed to all those possible blows and frictions

which the burrowing involves!

[37] In addition to the numerous illustrations given by Mr. Sedgwick, here

is one which Colonel A. T. Fraser published in _Nature_ for Nov. 9,

1893, concerning two Hindoo dwarfs:--"In speech and intelligence the

dwarfs were indistinguishable from ordinary natives of India. From an

interrogation of one of them, it appeared that he belonged to a

family all the male members of which have been dwarfs for several

generations. They marry ordinary native girls, and the female

children grow up like those of other people. The males, however,

though they develop at the normal rate until they reach the age of

six, then cease to grow, and become dwarfs."

[38] This remarkable case appears to militate against the conclusion,

drawn a few pages back, that the increase of a peculiarity by

coincidence of "spontaneous variations" in successive generations, is

very improbable; and that the special superiorities of musical

composers cannot have thus arisen. The reply is that the extreme

frequency of the occurrence among so narrow a class as that of

musical composers, forbids the interpretation thus suggested.

[39] I omitted to name here a cause which may be still more potent in

producing irregularity in the results of cousin-marriages. So far as

I can learn, no attempt has been made to distinguish between such

results as arise when the related parents from whom the cousins

descend are of the same sex and those which arise when they are of

different sexes. In the one case two sisters have children who

intermarry; and in the other case a brother and a sister have

children who intermarry. The marriages of cousins in these two cases

may be quite dissimilar in their results. If there is a tendency to

limitation of heredity by sex--if daughters usually inherit more from

the mother than sons do, while sons inherit more from the father than

from the mother, then two sisters will on the average of cases be

more alike in constitution than a sister and a brother. Consequently

the descendants of two sisters will differ less in their

constitutions than the descendants of a brother and a sister; and

marriage in the first case will be more likely to prove injurious

from absence of dissimilarity in the physiological units than

marriage in the second. My own small circle of friends furnishes

evidence tending to verify this conclusion. In one instance two

cousins who intermarried are children of two sisters, and they have

no offspring. In another the cousins who intermarried are children of

two brothers, and they have no offspring. In the third case the

cousins were descendants of two brothers and only one child resulted.

[40] _A propos_ of this sentence one of my critics writes:--"I cannot find

in this book the statement as first made that the 'life of an

individual is maintained by the unequal and ever-varying actions of

incident forces on its different parts.' Recent physiological work

offers a startling example of the statement."

To the question contained in the first sentence the answer is that I

have not made the statement in the above words, but that it is

implied in the chapter entitled "The Degree of Life varies as the

Degree of Correspondence," and more especially in § 36, which,

towards its close, definitely involves the statement. The verifying

evidence my critic gives me is this:--

"Prof. Sherrington has shown that if the sensory roots of the spinal

nerves are cut one by one there is at first no general effect

produced. That is to say, the remainder of the nervous system

continues to function as before. This condition (lack of general

effect) persists until about six pairs have been cut. With the

severance of the seventh pair, however, the whole central nervous

system ceases to function, so that stimulation of intact sensory

nerves produces no reflex action. After a variable period, but one of

many hours duration, the power of functioning is recovered. That is

to say, if the sensory impulses (from the skin, &c.) reaching the

central nervous system are rapidly reduced in amount, there comes a

point where those remaining do not suffice to keep the structure

'awake.' After a time, however, it adjusts itself to work with the

diminished supply. Similarly Strumpell describes the case of a boy

'whose sensory inlets were all paralyzed except one eye and one ear.'

When these were closed he instantly fell asleep."

[41] Fifty years before the discovery of the Röntgen rays and those

habitually emanating from uranium, it had been observed by Moser that

under certain conditions the surfaces of metals receive permanent

impressions from appropriate objects placed upon them. Such facts

show that the molecules of substances propagate in all directions

special ethereal undulations determined by their special

constitutions.

[42] This classification, and the three which follow it, I quote

(abridging some of them) from Prof. Agassiz's "Essay on

Classification."

[43] For explanations, see "Illogical Geology," _Essays_, Vol. I. How much

we may be misled by assuming that because the remains of creatures of

high types have not been found in early strata, such creatures did

not exist when those strata were formed, has recently (1897) been

shown by the discovery of a fossil Sea-cow in the lower Miocene of

Hesse-Darmstadt. The skeleton of this creature proves that it

differed from such Sirenian mammals as the existing Manatee only in

very small particulars: further dwindling of disused parts being an

evident cause. The same is true as regards, now, we consider that

since the beginning of Miocene days this aberrant type of mammal has

not much increased its divergence from the ordinary mammalian type;

if we then consider how long it must have taken for this large

aquatic mammal (some eight or ten feet long) to be derived by

modification from a land-mammal; and if then we contemplate the

probable length of the period required for the evolution of that

land-mammal out of a pre-mammalian type; we seem carried back in

thought to a time preceding any of our geologic records. We are shown

that the process of organic evolution has most likely been far slower

than is commonly supposed.

[44] Since this passage was written, in 1863, there has come to light much

more striking evidence of change from a more generalized to a less

generalized type during geologic time. In a lecture delivered by him

in 1876, Prof. Huxley gave an account of the successive modifications

of skeletal structure in animals allied to the horse. Beginning with

the _Orohippus_ of the Eocene formation, which had four complete toes

on the front limb and three toes on the hind limb, he pointed out the

successive steps by which in the _Mesohippus_, _Miohippus_,

_Protohippus_, and _Pliohippus_, there was a gradual approach to the

existing horse.

[45] Several of the arguments used in this chapter and in that which

follows it, formed parts of an essay on "The Development Hypothesis,"

originally published in 1852.

[46] _Studies from the Morphological Laboratory in the University of

Cambridge_, vol. vi, p. 84.

[47] _Ibid._, p. 81.

[48] _Studies from the Morphological Laboratory in the University of

Cambridge_, vol. vi, p. 89.

[49] Early in our friendship (about 1855) Prof. Huxley expressed to me his

conviction that all the higher articulate animals have twenty

segments or somites. That he adhered to this view in 1880, when his

work on _The Crayfish_ was published, is shown by his analysis there

given of the twenty segments existing in this fluviatile crustacean;

and adhesion to it had been previously shown in 1877, when his work

on _The Anatomy of Invertebrated Animals_ was published. On p. 398 of

that work he writes:--"In the abdomen there are, at most, eleven

somites, none of which, in the adult, bear ambulatory limbs. Thus,

assuming the existence of six somites in the head, the normal number

of somites in the body of insects will be twenty, as in the higher

_Crustacea_ and _Arachnida_." To this passage, however, he puts the

note:--"It is open to question whether the podical plates represent a

somite; and therefore it must be recollected that the total number of

somites, the existence of which can be actually demonstrated in

insects, is only seventeen, viz., four for the head, three for the

thorax, and ten for the abdomen." I have changed the number twenty,

which in the original edition occurred in the text, to the number

seventeen in deference to suggestions made to me; though I find in

Dr. Sharp's careful and elaborate work on the _Insecta_, that

Viallanes and Cholodkovsky agree with Huxley in believing that there

are six somites in the insect-head. The existence of a doubt on this

point, however, does not essentially affect the argument, since there

is agreement among morphologists respecting the _constancy_ of the

total number of somites in insects.

[50] To avoid circumlocution I let these words stand, though they are not

truly descriptive; for the prosperity of imported species is largely,

if not mainly, caused by the absence of those natural enemies which

kept them down at home.

[51] While these pages are passing through the press (in 1864), Dr. Hooker

has obliged me by pointing out that "plants afford many excellent

examples" of analogous transitions. He says that among true "water

plants," there are found, in the same species, varieties which have

some leaves submerged and some floating; other varieties in which

they are all floating; and other varieties in which they are all

submerged. Further, that many plants characterized by floating

leaves, and which have all their leaves floating when they grow in

deeper water, are found with partly aerial leaves when they grow in

shallower water; and that elsewhere they occur in almost dry soil

with all their leaves aerial.

[52] It will be seen that the argument naturally leads up to this

expression--Survival of the Fittest--which was here used for the

first time. Two years later (July, 1866) Mr. A. R. Wallace wrote to

Mr. Darwin contending that it should be substituted for the

expression "Natural Selection." Mr. Darwin demurred to this proposal.

Among reasons for retaining his own expression he said that I had

myself, in many cases, preferred it--"continually using the words

Natural Selection." (_Life and Letters_, &c., vol. III, pp. 45-6.)

Mr. Darwin was quite right in his statement, but not right in the

motive he ascribed to me. My reason for frequently using the phrase

"Natural Selection," after the date at which the phrase "Survival of

the Fittest" was first used above, was that disuse of Mr. Darwin's

phrase would have seemed like an endeavour to keep out of sight my

own indebtedness to him, and the indebtedness of the world at large.

The implied feeling has led me ever since to use the expressions

Natural Selection and Survival of the Fittest with something like

equal frequency.

[53] I am indebted to Mr. [now Sir W.] Flower for the opportunity of

examining the many skulls in the Museum of the College of Surgeons

for verification of this. Unfortunately the absence, in most cases,

of some or many teeth, prevented me from arriving at that specific

result which would have been given by weighing a number of the under

jaws in each race. Simple inspection, however, disclosed a

sufficiently-conspicuous difference. The under jaws of Australians

and Negroes, when collated with those of Englishmen, were visibly

larger, not only relatively but absolutely. One Australian jaw only

seemed about of the same size as an average English jaw; and this

(probably the jaw of a woman), belonging as it did to a smaller

skull, bore a greater ratio to the whole body of which it formed

part, than did an English jaw of the same actual size. In all the

other cases, the under jaws of these inferior races (containing

larger teeth than our own) were _absolutely_ more massive than our

own--often exceeding them in all dimensions; and _relatively_ to

their smaller skeletons were much more massive. Let me add that the

Australian and Negro jaws are thus strongly contrasted, not with all

British jaws, but only with the jaws of the civilized British. An

ancient British skull in the collection possesses a jaw almost or

quite as massive as those of the Australian skulls. All this is in

harmony with the alleged relation between greater size of jaws and

greater action of jaws, involved by the habits of savages.

[In 1891 Mr. F. Howard Collins carefully investigated this matter:

measuring ten Australian, ten Ancient British, and ten recent English

skulls in the College of Surgeons Museum. The result proved an

absolute difference of the kind above indicated, and a far greater

relative difference. To ascertain this last a common standard of

comparison was established--an equal size of skull in all the cases;

and then when the relative masses or cubic sizes of the jaws were

calculated, the result which came out was this:--Australian jaw,

1948; Ancient British jaw, 1135; Recent English jaw, 1030. "Hence,"

in the words of Mr. Collins, "the mass of the Recent English jaw is,

roughly speaking, half that of the Australian relatively to that of

the skull, and a ninth less than that of the Ancient British." He

adds verifying evidence from witnesses who have no hypothesis to

support--members of the Odontological Society. The Vice-President,

Mr. Mummery, remarks of the Australians that "the jaw-bones are

powerfully developed, and large in proportion to the cranium."]

[54] As bearing on the question of the varieties of Man, let me here refer

to a paper on "The Origin of the Human Races" read before the

Anthropological Society, March 1st, 1864, by Mr. Alfred Wallace. In

this paper, Mr. Wallace shows that along with the attainment of that

intelligence implied by the use of implements, clothing, &c., there

arises a tendency for modifications of brain to take the place of

modifications of body: still, however, regarding the natural

selection of spontaneous variations as the cause of the

modifications. But if the foregoing arguments be valid, natural

selection here plays but the secondary part of furthering the

adaptations otherwise caused. It is true that, as Mr. Wallace argues,

and as I have myself briefly indicated (see _Westminster Review_, for

April, 1852, pp. 496-501), the natural selection of races leads to

the survival of the more cerebrally-developed, while the less

cerebrally-developed disappear. But though natural selection acts

freely in the struggle of one society with another; yet, among the

units of each society, its action is so interfered with that there

remains no adequate cause for the acquirement of mental superiority

by one race over another, except the inheritance of

functionally-produced modifications.

[55] _Darwin and after Darwin_, Part II, p. 99.

[56] _Essays upon Heredity_, vol. i, p. 90.

[57] In a letter published by Dr. Romanes in _Nature_, for April 26, 1894,

he alleges three reasons why "as soon as selection is withdrawn from

an organ the _minus_ variations of that organ outnumber the _plus_

variations." The first is that "the survival-mean must descend to the

birth-mean." The interpretation of this is that if the members of a

species are on the average born with an organ of the required size,

and if they are exposed to natural selection, then those in which the

organ is relatively small will some of them die, and consequently the

mean size of the organ at adult age will be greater than at birth.

Contrariwise, if the organ becomes useless and natural selection does

not operate on it, this difference between the birth-mean and the

survival-mean disappears. Now here, again, the _plus_ variations and

their effects are ignored. Supposing the organ to be useful, it is

tacitly assumed that while _minus_ variations are injurious, _plus_

variations are not injurious. This is untrue. Superfluous size of an

organ implies several evils:--Its original cost is greater than

requisite, and other organs suffer; the continuous cost of its

nutrition is unduly great, involving further injury; it adds

needlessly to the weight carried and so again is detrimental; and

there is in some cases yet a further mischief--it is in the way.

Clearly, then, those in which _plus_ variations of the organ have

occurred are likely to be killed off as well as those in which

_minus_ variations have occurred; and hence there is no proof that

the survival-mean will exceed the birth-mean. Moreover the assumption

has a fatal implication. To say that the survival-mean of an organ is

greater than the birth-mean is to say that the organ is greater _in

proportion to other organs_ than it was at birth. What happens if

instead of one organ we consider all the organs? If the survival-mean

of a particular organ is greater than its birth-mean, the survival

mean of each other organ must also be greater. Thus the proposition

is that every organ has become larger in relation to every other

organ!--a marvellous proposition. I need only add that Dr. Romanes'

inferences with respect to the two other causes--atavism and failing

heredity--are similarly vitiated by ignoring the plus variations and

their effects.

[58] _Westminster Review_, January, 1860. See also _Essays, &c._, vol. i,

p. 290.

[59] "On Orthogenesis and the Impotence of Natural Selection in

Species-Formation," pp. 2, 19, 22, 24.

[60] Address to Plymouth Institution, at opening of Session 1895-6.

[61] _Westminster Review_, April, 1857. "Progress: its Law and Cause." See

also _Essays_, vol. i.

[62] It may be needful to remark, that by the proposed expression it is

intended to define--not Life in its essence; but, Life as manifested

to us--not Life as a _noumenon_: but, Life as a _phenomenon_. The

ultimate mystery is as great as ever: seeing that there remains

unsolved the question--What _determines_ the co-ordination of

actions?

[63] _Prin. of Phys._, 2nd edit., p. 77.

[64] _Ibid._, 3rd edit., p 249.

[65] _Ibid._, p. 124.

[66] Agassiz and Gould, p. 274.

[67] _Prin. of Phys._, 3rd edit., p. 964.

[68] "Parthenogenesis," p. 8.

[69] _Prin. of Phys._, p. 92.

[70] _Ibid._, p. 93.

[71] _Ibid._, p. 917.

[72] "A General Outline of the Animal Kingdom." By Prof. T. R. Jones, F.

G. S., p. 61.

[73] Carpenter.

[74] _Prin. of Phys._, p. 873.

[75] _Ibid._, p. 203.

[76] _Ibid._, p. 209.

[77] _Ibid._, p. 249.

[78] _Ibid._, p. 249.

[79] _Ibid._, p. 250.

[80] _Prin. of Phys._, p. 256.

[81] _Ibid._, p. 212.

[82] _Ibid._, p. 266.

[83] _Prin. of. Phys._, p. 267.

[84] _Ibid._, p. 276.

[85] _Ibid._, 2nd edit., p. 115.

[86] _Prin. of Phys._, p. 954.

[87] _Ibid._, p. 958.

[88] _Ibid._, p. 688.

[89] _Ibid._, p. 958.

[90] "A General Outline of the Animal Kingdom." By Professor T. R. Jones,

p. 61.

[91] _Prin. of Phys._, p. 907.

[92] Should it be objected that in the higher plants the sperm-cell and

germ-cell differ, though no distinct co-ordinating system exists, it

is replied that there _is_ co-ordination of actions, though of a

feeble kind, and that there must be some agency by which this is

carried on.

[93] It is a significant fact that amongst the dioecious invertebrata,

where the nutritive system greatly exceeds the other systems in

development, the female is commonly the largest, and often greatly

so. In some of the Rotifera the male has no nutritive system at all.

See _Prin. of Phys._, p. 954.

[94] _Prin. of Phys._, p. 908.

[95] "Parthenogenesis," pp. 66, 67.

[96] "Lectures on Animal Chemistry." By Dr. Bence Jones. _Medical

Times_, Sept. 13th, 1851. See also _Prin. of Phys._, p. 171.

[97] _Cyclopædia of Anatomy and Physiology_, Vol. IV, p. 506.

[98] From a remark of Drs. Wagner and Leuckart this chemical evidence

seems to have already suggested the idea that the sperm-cell becomes

"metamorphosed into the central parts of the nervous system." But

though they reject this assumption, and though the experiments of Mr.

Newport clearly render it untenable, yet none of the facts latterly

brought to light conflict with the hypothesis that the sperm-cell

contains unorganized co-ordinating matter.

[99] Quain's _Elements of Anatomy_, p. 672.

[100] The maximum weight of the horse's brain is 1 lb. 7 ozs.; the human

brain weighs 3 lbs., and occasionally as much as 4 lbs.; the brain of

a whale, 75 feet long, weighed 5 lbs. 5 ozs.; and the elephant's

brain reaches from 8 lbs. to 10 lbs. Of the whale's fertility we know

nothing; but the elephant's quite agrees with the hypothesis. The

elephant does not attain its full size until it is thirty years old,

from which we may infer that it arrives at a reproductive age later

than man does; its period of gestation is two years, and it produces

one at a birth. Evidently, therefore, it is much less prolific than

man. See Müller's _Physiology_ (Baly's translation), p. 815, and

Quain's _Elements of Anatomy_, p. 671.

[101] That the size of the nervous system is the measure of the ability to

maintain life, is a proposition that must, however, be taken with

some qualifications. The ratio between the amounts of gray and white

matter present in each case is probably a circumstance of moment.

Moreover, the temperature of the blood may have a modifying

influence; seeing that small nervous centres exposed to rapid

oxidation will be equivalent to larger ones more slowly oxidized.

Indeed, we see amongst mankind, that though, in the main, size of

brain determines mental power, yet temperament exercises some

control. There is reason to think, too, that certain kinds of nervous

action involve greater consumption of nervous tissue than others; and

this will somewhat complicate the comparisons. Nevertheless, these

admissions do not affect the generalization as a whole, but merely

prepare us to meet with minor irregularities.

[102] Let me here note in passing a highly significant implication. The

development of nervous structures which in such cases take place,

cannot be limited to the finger-ends. If we figure to ourselves the

separate sensitive areas which severally yield independent feelings,

as constituting a network (not, indeed, a network sharply marked out,

but probably one such that the ultimate fibrils in each area intrude

more or less into adjacent areas, so that the separations are

indefinite), it is manifest that when, with exercise, the structure

has become further elaborated, and the meshes of the network smaller,

there must be a multiplication of fibres communicating with the

central nervous system. If two adjacent areas were supplied by

branches of one fibre, the touching of either would yield to

consciousness the same sensation: there could be no discrimination

between points touching the two. That there may be discrimination,

there must be a distinct connection between each area and the tract

of grey matter which receives the impressions. Nay more, there must

be, in this central recipient-tract, an added number of the separate

elements which, by their excitements, yield separate feelings. So

that this increased power of tactual discrimination implies a

peripheral development, a multiplication of fibres in the

trunk-nerve, and a complication of the nerve-centre. It can scarcely

be doubted that analogous changes occur under analogous conditions

throughout all parts of the nervous system--not in its sensory

appliances only, but in all its higher co-ordinating appliances, up

to the highest.

[103] _Essays upon Heredity_, p. 87.

[104] _Les Maladies des Vers à soie_, par L. Pasteur, Vol. I, p. 39.

[105] Curiously enough, Weismann refers to, and recognizes, syphilitic

infection of the reproductive cells. Dealing with Brown-Séquard's

cases of inherited epilepsy (concerning which, let me say, that I do

not commit myself to any derived conclusions), he says:--"In the case

of epilepsy, at any rate, it is easy to imagine [many of Weismann's

arguments are based on things 'it is easy to imagine'] that the

passage of some specific organism through the reproductive cells may

take place, as in the case of syphilis" (p. 82). Here is a sample of

his reasoning. It is well known that epilepsy is frequently caused by

some peripheral irritation (even by the lodging of a small foreign

body under the skin), and that, among peripheral irritations causing

it, imperfect healing is one. Yet though, in Brown-Séquard's cases, a

peripheral irritation caused in the parent by local injury was the

apparent origin, Weismann chooses gratuitously to assume that the

progeny were infected by "some specific organism," which produced the

epilepsy! And then though the epileptic virus, like the syphilitic

virus, makes itself at home in the egg, the parental protoplasm is

not admitted!

[106] _Philosophical Transactions of the Royal Society for the Year 1821_,

Part I, pp. 20-24.

[107] It will, I suppose, be said that the non-inheritance of mutilations

constitutes evidence of the kind here asked for. The first reply is

that the evidence is conflicting, as it may well be. It is forgotten

that to have valid evidence of non-inheritance of mutilations, it is

requisite that both parents shall have undergone mutilation, and that

this does not often happen. If they have not, then, assuming the

inheritableness of mutilations, there would, leaving out other

causes, be an equal tendency to appearance and non-appearance of the

mutilation in offspring. But there is another cause--the tendency to

reversion, which ever works in the direction of cancelling individual

characters by the return to ancestral characters. So that even were

the inheritance of mutilations to be expected (and for myself I may

say that its occurrence surprises me), it could not be reasonably

looked for as more than exceptional: there are two strong

countervailing tendencies. But now, in the second place, let it be

remarked that the inheritance or non-inheritance of mutilations is

beside the question. The question is whether modifications of parts

produced by modifications of functions are inheritable or not. And

then, by way of disproof of their inheritableness, we are referred to

cases in which the modifications of parts are not produced by

modifications of functions, but are otherwise produced!

[108] See _First Principles_, Part II, Chap. XXII, "Equilibration."

[109] _Principles of Biology_, § 46, (No. 8. April, 1863).

[110] _Ibid._ This must not be understood as implying that while the mass

increases as the cubes, the _quantity of motion_ which can be

generated increases only as the squares; for this would not be true.

The quantity of motion is obviously measured, not by the sectional

areas of the muscles alone, but by these multiplied into their

lengths, and therefore increases as the cubes. But this admission

leaves untouched the conclusion that the ability to _bear stress_

increases only as the squares; and thus limits the ability to

generate motion, by relative incoherence of materials.

[111] _The Transactions of the Linnæan Society of London_, Vol. XXII, p.

215. The estimate of Reaumur, cited by Kirby and Spence, is still

higher--"in five generations one Aphis may be the progenitor of

5,904,900,000 descendants; and that it is supposed that in one year

there may be twenty generations." (_Introduction to Entomology_, Vol.

I, p. 175)

[112] _A Manual of the Anatomy of Invertebrated Animals_, by T. H. Huxley,

p. 206.

[113] Respecting the _Eloidea_ I learn that in 1879--thirty years after it

had become a pest--one solitary male plant was found in a pond near

Edinburgh; but "in an exhaustive inquiry on the plant made by Dr.

Groenland, of Copenhagen, he could find no trace of any male

specimens having been found in Europe other than the Scotch." In

waters from which the _Eloidea_ has disappeared, it seems to have

done so in consequence of the growth of an _Alga_, which has produced

turbid water unfavourable to it. That is to say, the decreased

multiplication of somatic cells in some cases, is not due to any

exhaustion, but is caused by the rise of enemies or adverse

conditions; as happens generally with introduced species of plants

and animals which multiply at first enormously, and then, without any

loss of reproductive power, begin to decrease under the antagonizing

influences which grow up.

[114] _A Text Book of Human Physiology._ By Austin Flint, M.D., LL.D.

Fourth edition. New York: D. Appleton & Co. 1888. Page 797.

[115] This supposition I find verified by Mr. A. S. Packard in his

elaborate monograph on "The Cave Fauna of North America, &c.," as

also in his article published in the _American Naturalist_,

September, 1888; for he there mentions "variations in _Pseudotremia

cavernarum_ and _Tomocerus plumbeus_, found living near the entrance

to caves in partial daylight." The facts, as accumulated by Mr.

Packard, furnished a much more complete answer to Prof. Lankester

than is above given, as, for example, the "blindness of _Neotoma_, or

the Wood-Rat of Mammoth Cave." It seems that there are also "cave

beetles, with or without rudimentary eyes," and "eyeless spiders" and

Myriapods. And there are insects, as some "species of Anophthalmus

and Adelops, whose larvæ are lacking in all traces of eyes and optic

nerves and lobes." These instances cannot be explained as sequences

of an inrush of water carrying with it the remote ancestors, some of

which did not find their way out; nor can others of them be explained

by supposing an inrush of air, which did the like.

[116] See "Social Organism" in _Westminster Review_ for January, 1860; also

_Principles of Sociology_, § 247.

[117] _Contemporary Review_, September, 1893.

[118] _Evolution of Sex_, p. 50.

[119] _Souvenirs Entomologiques_, 3^{me} Série, p. 328.

[120] _Natural History of Bees_, new ed., p. 33.

[121] _Origin of Species_, 6th ed., p. 232.

[122] _Contemporary Review_, September, 1893, p. 333.

[123] _The Entomologist's Monthly Magazine_, March, 1892, p. 61.

[124] Perhaps it will be alleged that nerve-matter is costly, and that this

minute economy might be of importance. Anyone who thinks this will no

longer think it after contemplating a litter of half-a-dozen young

rabbits (in the wild rabbit the number varies from four to eight);

and on remembering that the nerve-matter contained in their brains

and spinal cords, as well as the materials for building up the bones,

muscles, and viscera of their bodies, has been supplied by the doe in

the space of a month; at the same time that she has sustained herself

and carried on her activities: all this being done on relatively poor

food. Nerve-matter cannot be so very costly then.

[125] _Loc. cit._, p. 318.

[126] _The Germ Plasm_, p. 54.

[127] While Professor Weismann has not dealt with my argument derived from

the distribution of discriminativeness on the skin, it has been

criticized by Mr. McKeen Cattell, in the last number of _Mind_

(October, 1893). His general argument, vitiated by extreme

misconceptions, I need not deal with. He says:--"Whether changes

acquired by the individual are hereditary, and if so to what extent,

is a question of great interest for ethics no less than for biology.

But Mr. Spencer's application of this doctrine to account for the

origin of species [!] simply begs the question. He assumes useful

variations [!]--whether of structure or habit is immaterial--without

attempting to explain their origin": two absolute misstatements in

two sentences! The only part of Mr. Cattell's criticism requiring

reply is that which concerns the "sensation-areas" on the skin. He

implies that since Weber, experimental psychologists have practically

set aside the theory of sensation areas: showing, among other things,

that relatively great accuracy of discrimination can be quickly

acquired by "increased interest and attention.... Practice for a few

minutes will double the accuracy of discrimination, and practice on

one side of the body is carried over to the other." To me it seems

manifest that "increased interest and attention" will not enable a

patient to discriminate two points where a few minutes before he

could perceive only one. That which he can really do in this short

time is to learn to discriminate between the _massiveness of a

sensation_ produced by two points and the massiveness of that

produced by one, and to _infer_ one point or two points accordingly.

Respecting the existence of sensation-areas marked off from one

another, I may, in the first place, remark that since the eye

originates as a dermal sac, and since its retina is a highly

developed part of the sensitive surface at large, and since the

discriminative power of the retina depends on the division of it into

numerous rods and cones, each of which gives a separate

sensation-area, it would be strange were the discriminative power of

the skin at large achieved by mechanism fundamentally different. In

the second place I may remark that if Mr. Cattell will refer to

Professor Gustav Retzius's _Biologische Untersuchungen_, New Series,

vol. iv (Stockholm, 1892), he will see elaborate diagrams of

superficial nerve-endings in various animals showing many degrees of

separateness. I guarded myself against being supposed to think that

the sensation-areas are sharply marked off from one another; and

suggested, contrariwise, that probably the branching

nerve-terminations intruded among the branches of adjacent

nerve-terminations. Here let me add that the intrusion may vary

greatly in extent; and that where the intruding fibres run far among

those of adjacent areas, the discriminativeness will be but small,

while it will be great in proportion as each set of branching fibres

is restricted more nearly to its own area. All the facts are

explicable on this supposition.

[128] To save space and exclude needless complication I have omitted these

passages from the preceding divisions of this appendix.

[129] Though Professor Weismann does not take up the challenge, Dr. Romanes

does. He says:--"When selection is withdrawn there will be no

excessive _plus_ variations, because so long as selection was present

the efficiency of the organ was maintained at its highest level: it

was only the _minus_ variations which were then eliminated"

(_Contemporary Review_, p. 611). In the first place, it seems to me

that the phrases used in this sentence beg the question. It says that

"the efficiency of the organ was maintained at its _highest_ level";

which implies that the highest level (tacitly identified with the

greatest size) is the best and that the tendency is to fall below it.

This is the very thing I ask proof of. Suppose I invert the idea and

say that the organ is maintained at its right size by natural

selection, because this prevents increase beyond the size which is

best for the organism. Every organ should be in due proportion, and

the welfare of the creature as a whole is interfered with by excess

as well as by defect. It may be directly interfered with--as for

instance by too big an eyelid; and it may be indirectly interfered

with, where the organ is large, by needless weight and cost of

nutrition. In the second place the question which here concerns us is

not what natural selection will do with variations. We are concerned

with the previous question--What variations will arise? An organ

varies in all ways; and, unless reason to the contrary is shown, the

assumption must be that variations in the direction of increase are

as frequent and as great as those in the direction of decrease. Take

the case of the tongue. Certainly there are tongues inconveniently

large, and probably tongues inconveniently small. What reason have we

for assuming that the inconveniently small tongues occur more

frequently than the inconveniently large ones? None that I can see.

Dr. Romanes has not shown that when natural selection ceases to act

on an organ the _minus_ variations in each new generation will exceed

the _plus_ variations. But if they are equal the alleged process of

panmixia has no place.

[130] _The Variation of Animals and Plants under Domestication_, vol. ii,

p. 292.

[131] _Journal of the Anthropological Institute_ for 1885, p. 253.

[132] In "The All-Sufficiency of Natural Selection" (_Contemporary Review_,

Sept., 1893, p. 311), Professor Weismann writes:--"I have ever

contended that the acceptance of a principle of explanation is

justified, if it can be shown that without it certain facts are

inexplicable." Unless, then, Prof. Weismann can show that the

distribution of discriminativeness is otherwise explicable, he is

bound to accept the explanation I have given, and admit the

inheritance of acquired characters.

[133] Prof. Weismann is unaware that the view here ascribed to Roux,

writing in 1881, is of far earlier date. In the _Westminster Review_

for January, 1860, in an essay on "The Social Organism," I

wrote:--"One more parallelism to be here noted, is that the different

parts of a social organism, like the different parts of an individual

organism, compete for nutriment; and severally obtain more or less of

it according as they are discharging more or less duty." (See also

_Essays_, i, 290.) And then, in 1876, in _The Principles of

Sociology_, vol. i, § 247, I amplified the statement thus:--"All

other organs, therefore, jointly and individually, compete for blood

with each organ ... local tissue-formation (which under normal

conditions measures the waste of tissue in discharging function) is

itself a cause of increased supply of materials ... the resulting

competition, not between units simply, but between organs, causes in

a society, as in a living body, high nutrition and growth of parts

called into greatest activity by the requirements of the rest."

Though I did not use the imposing phrase

"intra-individual-selection," the process described is the same.

[134] _Proceedings of the Biological Society of Washington_, vol. ix.

[135] Romanes Lecture, p. 29.

[136] _Ibid._, p. 35.

[137] This interpretation harmonizes with a fact which I learn from Prof.

Riley, that there are gradations in this development, and that in

some species the ordinary neuters swell their abdomens so greatly

with food that they can hardly get home.